US1432022A - Circuit connection of electron discharge apparatus - Google Patents

Description

R. A. HEISING.

CIRCUIT CONNECTION 0F ELECTRON DISCHARGE APPARATUS.

APPLICATION FILED own. 1916.

1,432,022, Patented Oct. 17,1922.

/1 1/6/7701 Raymond A. He/s 017.

b I h Patented Oct 17,1922.

TED STATES RAYMOND A. nmsme, or EASTORANGE, new JERSEY, assronon 'ro wns'mart ELECTRIC COMPANY, mconronarnn, or NEW YORK, N. 1., A CORPORATION 0F new YORK.

omcurr commoner: or ELECTRON DISCHARGE arraaarus.

To all whom it may concern:

Be it known that I, RAYMOND A. HEIsINc, a citizen of the United States, residing at East Orange, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Circuit Connections of Electron Discharge Apparatus, of which the following is a full, clear, concise, and exact description.

This invention relates to circuit connections for electron discharge apparatus and more especially to electron discharge apparatus of the. type in which a filamentary cathode enclosed in an evacuated vessel is provided with means for heating the filament to incandescence to cause it to emit electrons, which may serve to convey a space current to a cooperating anode enclosed in the same envelope. Such devices may be used for producing X-ray or rectifying alternating currents, or when provided with a controlling grid, as in vacuum tubes of the audion type, for amplifying variable currents, detecting wireless signals, and for various other purposes.

It has been customary prior to my invention to provide, for heating the cathode, a direct current source, such as a battery or direct current generator. The external circuit connections to the cathode have been generally made to one side of the filament, and as a result all parts of the filament have not been of the same otential with respect to the anode or the grid, the difference between extreme ends being equal to the voltage impressed upon the filament. Where a'source 'of direct current is employed, this voltage or difi'erence of potential is constant, and therefore will not produce variations in the operation of the device. It is, however, more convenient in some cases to employ an alternating current for heating the filament,

this being particularly true when a large number of suchtubes are operated simultaneously, requiring a considerable amount of power for the heating of the filament. Upon the substitution of such an alternating current heating source for the filament, the variations of potential difference between the grid and filament or the plate and filament which are thereby introduced,

potential of the filament with grid 13, and the other terminal connected to Application filed October 11,1916. Serial No. 124,953.

may seriously affect the efiicient operation of the device. 5

The object of this invention is to provide an improved clrcuit connection for electron dlscharge devices whereby alternating current may be employed forheating the filament, and the disadvantage above mentioned, as well as others which will hereafter appear, may be overcome.

In the practical application of my invention, current for heating the filament is obtamed directly from an alternatingcurrent, generator or from the secondary of a transorme'r, and the connections from anode and grid to the cathode are made to some point in the filament circuit which has a potential equal to the average potential of the filament which in eneral is that of the middle point of the filament. When the connec tions are made in this way, the average voltage or difierence of potential at any instant between different portions of the cathode and the grid, and the anode, due to the heating current, will be zero.

The invention will be better understood by reference to the accompanying drawing and following specification, in which Fig. 1 represents an embodiment of this invention shown in connection with an electron discharge device; Fig. 2 is a modification of Fig. 1; Fig. 3 shows how this invention may be applied simultaneously to a pluralit of electron discharge devices; and Fig. 4. i lustrates how a non-inductive resistance may be employed to obtain the desired average respect to the grid and cathode.

Referring to Fig. 1, there is shown a vacuum tube .10 of the audion type containing the usual heated filament 12, grid 13 and plate 14.. Connected to the input terminals 12 and 13, is some'source of variable .currents to be amplified or rectified or otherwise operated upon. In this case there-is shown a microphone transmitter 16 in circuit with a battery 17 and the primary 18 of the transformer 19. The secondary 20 of said transformer has. one terminal connected to the the filament 12 in a-manner hereafter described. Across the terminals of the secondi ary winding 20 is connected a resistance 21 for the purpose of makin the impedance of the input circuit, as viewed from the primary coil 18, the same for all impressed fre quencies. The output circuit is of any wellknown form, such as that shown, and com,-

prises a source of direct current 24 and the connection of the filament to the external circuits, in view of the prior art would be to connect one terminal of the coil 20 and the negative pole of the battery 24 to one terminal of the filament. This, however, leads to the disadvantages mentioned above,-that there will be continual variations in the potential between the filament and grid, and between the filament and plate. To overcome this disadvantage, a connection is made from the middle point of the filament 12, as shown. at 31, to a point 32 comm'on.to both the input and output circuits. As a result,

the average voltage or difference of potential between different portions of the cathode and grid and anode, due to the heating current, will be zero.

One inconvenience of the arran ement as shown in Fig. 1 is the necessity of aving an additional terminal comin through the yvall of the vacuum tube 10. his inconvenience may be overcome by arranging the circuit as shown in Fig. '2. In this circuit there is shown a similar source of alternating currents adapted to be used as the input of a tube 35, the said tube bein similar in every respect to that shown in ig. 1. The external circuit, comprising the input and the output circuits, is also similar in every respect. In this Fig. 2, however, the point 32 of the circuit, which is common to both the input and the output circuits, is connected to the'middle point of the secondary 36 of the transformer 37. The primary 38of.this transformer is supplied from the alternating current generator 29, and in general it will be desirable to have some regulating device, such as39, to control the current delivered by the generator. In this case again the same purpose is accomplished as in Fig. 1,

namely, that the external circuits are connected to such a point in the filament circuit that the average difference of potential at any instant between difi'erenhportions of the cathode and grid and anode, due to the heating current, will be zero.

In this Fig. 2 there are shown two condensers 41 and 42, each connected across one half of the transformer secondary 36. These condensers are used for the purpose of aifording a low impedance path for the alternating currents in the input and output circuits, but they should be of such dimensions as to offer a reasonably high impedance to the alternating current from the generator 29.

- Referring to Fig. 3, the invention is shown adapted to a wireless system such as is described in the U. S. Patent No. 1,388,- 450 to C01 itts and Arnold, issued August 23, 1921. n this figure there is shown an incoming circuit 45, which, by mleans of the transformer 46, may impress suitable signals upon the input circuit of a bank of audion amplifiers 48. In eneral, for such a system as shown here, t e incoming signals will consist of high frequency oscillations modulated in accordance with low fre- I quency signals. Each of the. amplifiers 48 comprises the usual filaments, plates and grids. In this figure the filaments are s own as connected in parallel, and the plates are similarly shown as connected in parallel,and the grids are also shown as connected in paralleL- The usual direct our rent source 50 is supplied for the output circuit, this source consisting of stora e batteries or a direct current generator. T e output circuit is finally connected in a suitable manner to an antenna system 51, all in a manner fully described in theabove mentioned a plication of Colpitts andArnold.

The fi aments are shown in this figure as beingadapted tobe heated by an alternating current in accordance with thisinvention, the enerator 29 and transformer 37 being of the same form as. shown in Fig. 2. In some cases, however,'it may be inconvenient or impossible to make a connection to the middle point of the transformer secondary 36. Accordingly, there is placed across the terminals of said secondary an-impedance or choke coil 52, and from; the middle point of this impedance52 a connection is made to the point 32 common to the input and outut circuits of the amplifier system. The impedance of this coil is preferably sufliciently high to revent the passage of much current from t e generator 29, but should have a reasonably-small direct current impedance for the current from thebattery 50. As shown in the drawing, both halves of retard coil 52 are wound in the samedire'ction so that the retard coil acts non-inductively to signaling currents received from line45. As described in connection with Fig. 2, there are shown two condensers 53' and 54, each connected across-one-half of the impedance 52, these condensers being supplied to offer a low impedance path for the high frequency current to be amplified and transmitted from the antenna 51. As in Fig. 2,

. nectiofi from the point 32 to the middle of of said auto-transformer.

' that the transformer 37 of this Fig. 3 may therefore be dispensed with if the generator 29 is of a suitable volta e. Also this impedance 52 may, obvious y, be used in connection with the circuits of Fig. 1 or Fig. 2

either with or without the transformers shown in said circuits.

The impedance 52 may, furthermore, be

replaced by a non-inductive resistance such as shown in Fig. 4. In such a case the circuit connections will be similar in every respect, with the exception that the negative pole of the battery should be connected which the deleterious effects arisin to one end 56 of the resistance 54. This is preferable to having the connection made to the middle of the resistance 54, in order that the space current from the filament may pass directly to the battery 55 without having to pass through the high resistance 54. In view of the fact that the current in the input circuit is exceedingly small, it will be permissible to make the contact from the input circuit directly with the ,middle point 57 of the resistance 54. This arrangement has the disadvantage that the voltage between the filament and the anode will fluctuate slightl in view of the variable fall of potential a ong the half of the resistance from 56 to 57. Such dis-c advantage ma be overcome or neutralized, however, by s idin the pint of contact of the input circuit min t e point 57 to the point 58 slightly to one side, and by such an amount that the fall of potential between 57 and 58 multiplied by the amplifying coefii cient of the amplifier shall be equal and op-- posite to the fall of potential between the points 56 and 57.

A number of circuits have now been described, in each of which an alternating current is used for heating the filament or filaments of a vacuum tube system, and in ,from potential variations are overcome. t is to be understood, however, that the invention is not limited to the circuits shown, and that numerous changes may be madein the circuits without departing from the spirit of this invention. a

'What is claimed is:

1. The combination with an electron discharge device comprisin an evacuated envelope having therein a lamentary cathode and a cooperating anode, of a transformer connected to a source of alternatin current and having its secondary connecte to said cathode for heating it to incandescence, an

It is apparent external circuit connection between said anode and the central point in the secondary Winding of said transformer, and a condenser connected across each half of said secondary adapted to ofl'era low impedance path to input frequencies and a high impedance path to the heating generator frequency. v 2. The combination with a plurality of electron discharge devices of the audion type each comprising an evacuated envelope having a filamentary cathode and a discharge controlling grid, the grids being connected in parallel and the filaments being connected in parallel, of a transformer connected to a source'of alternating current and having its secondary connected to saidcathodes for heating them to incandescence, and an external connection from said grids to the cen t-ral point in the secondary winding of said transformer.

3. In combination a vacuum tube having an anode, a cathode and a control electrode, a. source of alternating current for heating said cathode, .an impedance between said source and said cathode, a connection between said control electrode and the midpoint of said impedance, and a condenser across said impedance. v

4. In combination a vacuum tube having an anode, a cathode and a control electrode,

a source of alternating current for heating said cathode, an impedance between said source and said cathode, a connection from the midpoint of said impedance to said control electrode. and a condenser across each half of said impedance.

5. An electron discharge device having a thermionic cathode and an input circuit, a transformer connected to said cathode for supplying heating current thereto, a path in shunt to the secondary of said transformer. and a connection from said input circuit to a point on said path having a potential substantially equal to the average cathode potential. i

6. An electron discharge device having a thermionic cathode and an output circuit, a transformer connected to said cathode for supplying heating current thereto, a path in shunt to the secondary of said transformer, and a connection from said output circuit to a point on said path having a potential substantially equal to the averagecathode potential.

thermionic cathode and an input and an output circuit, a transformer connected to said cathode for supplying heating current thereto, a path in shunt to. the secondary of said transformer, and a connection from said circuits to a point on said path having a potential substantially equal tothe average cathode otential.

8. Asignaling system comprising an electron disc arge device having a thermionic cathode, an input circuit and an output circuit a transformer connected to said cathode circuits ton point on said tential substantially equa to the average for supplying heating current thereto, a path cathode potential.

in shunt to the second former, said path bein to heating current and o naling currents, and a connection from said ury of said transof high impedance w impedance to si In witness whereof, I hereunto subscribe my name this 9th day of October,A. D. 1916;

RAYMOND A. HEISINGQ ath having a po-

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